Which vessels are exceptions to the general rule about oxygen content in blood vessels?

• A. Aorta and Vena Cava
• B. Hepatic Arteries and Veins
• C. Pulmonary artery and pulmonary veins
• D. Coronary Arteries and Veins

Answer: (C)

In systemic circulation, arteries carry oxygen-rich blood and veins carry oxygen-poor blood. The lungs are the only place where this pattern reverses: blood travels to the lungs via the pulmonary artery, which is still deoxygenated, and returns to the heart through the pulmonary veins, which are oxygenated. That reversal makes the pulmonary vessels the exception to the general rule.

The other options follow the usual pattern: the aorta and vena cava align with arterial and venous roles in the body’s circulation, and hepatic arteries and hepatic veins likewise reflect oxygenated input and deoxygenated drainage from the liver. The coronary vessels involve oxygenated blood to the heart muscle via coronary arteries and deoxygenated blood away via coronary veins, but this pair isn’t an exception to the general rule about vessel oxygen content.